A few take the words “fallen asleep” literally and believe that the dead remain unconscious until the Lord returns. But most see this as a euphemism: that the body “sleeps” while the spirit remains conscious. When Christians die, their bodies go into the grave while their spirits go to be with Jesus (see 2Co 5:6–8; Php 1:23). When unbelievers die, their bodies go into the grave while their spirits go to a place of torment.
The Old Testament speaks in a limited way about the grave, where all go at death. The New Testament uses the Greek word Hades for the Old Testament concept (see Rev 20:13), but expands on it considerably. Jesus hinted that Hades is divided into two parts—one for the wicked and one for the righteous. For the wicked it is described as torment, agony and fire; for the righteous it is comfort and rest (see Lk 16:22–26).
Gehenna is another word for hell, the final place of judgment upon the wicked. It was borrowed from the phrase meaning “the Valley of Hinnom,” a place where human sacrifices and pagan worship had occurred (see 2Ki 23:10). During New Testament times the place was the Jerusalem city dump where fires burned continually—a graphic image of perpetual torment and judgment.
When Christ returns, those who have died and are with Jesus will be given new bodies—resurrected, glorified bodies. At the final judgment unbelievers will be thrown into the “lake of fire” (Rev 20:11–15).